[PATCH v2 7/8] drm/i915/ttm: trust snooping when gen 6+ when deciding default cache_level

[Robert Beckett <bob.beckett@xxxxxxxxxxxxx>]

By default i915_ttm_cache_level() decides I915_CACHE_LLC if HAS_SNOOP.
this is divergent from existing backends code which only considers
HAS_LLC.
Testing shows that trusting snooping on gen5- is unreliable, so limit to
gen6+

Signed-off-by: Robert Beckett <bob.beckett@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
index 4c1de0b4a10f..e6cce35edb65 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -46,7 +46,9 @@ static enum i915_cache_level
 i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,
 		     struct ttm_tt *ttm)
 {
-	return ((HAS_LLC(i915) || HAS_SNOOP(i915)) &&
+	bool can_snoop = HAS_SNOOP(i915) && (GRAPHICS_VER(i915) > 5);
+
+	return ((HAS_LLC(i915) || can_snoop) &&
 		!i915_ttm_gtt_binds_lmem(res) &&
 		ttm->caching == ttm_cached) ? I915_CACHE_LLC :
 		I915_CACHE_NONE;
-- 
2.25.1